Type bar bearing



1960 H. 1.. THOLSTRUP 2,924,322

TYPE BAR BEARING Filed Feb. 18, 1959 INVENTOR.

H EN RY L. THOLSTRUP 8 I BY ATTORNEY TYPE BAR BEARING Henry L. Tholstrup, Rochester, N.Y., assignor to Commercial Controls Corporation, Rochester, N.Y., a corporation of Delaware Application February 18, 1959, Serial No. 794,121

Claims. (Cl. 197-38) This invention relates to an improved bearing for type bars.

The type bars of a typewriter are mounted in a type bar segment by a steel fulcrum wire which passes through a type bar fulcrum hole at the end of the type bar opposite the type head. The fulcrum wire, therefore, constitutes the bearing on which the type bars rock during the typing operation. Since the fulcrum wire is seated in a groove which follows the arc of the sector comprising the type segment, it is curved throughout its length with the result that the type bar fulcrum hole, which is cylindrical, is in point contact therewith rather than in the more ideal line contact. The point contact between the cylindrical type bar fulcrum hole and the conventional curved fulcrum wire results in such rapid wear of the type bar fulcrum hole that the type bars so mounted will not operate satisfactorily beyond about a half million operations before replacement becomes necessary.

It is, therefore, the principal object of this invention to provide a type bar bearing which will overcome the defiiciencies of the conventional structures and which will greatly extend the operating life of a type bar before replacement is required.

The objective of the invention is attained by providing a bearing insert for the type bar fulcrum hole, which insert is characterized by a true cylindrical bearing surface which provides for perfect line contact with the type bar fulcrum hole.

It is a further object of the invention to provide a larger bearing surface for a type bar than that heretofore provided by the conventional fulcrum wire. Withal, it is the purpose of the invention to provide an improved type bar bearing which is compatible with the design and dimensions of the type segments and fulcrum wires now in use.

It is still a further object of the invention to provide an improved type bar bearing which can be cheaply produced and installed in typewriters without substantial modification of existing typewriter elements.

These and other objects and advantages of the invention will appear from a perusal of the description which is to follow when read in light of the drawings forming a part hereof, in which drawings like reference numerals indicate like parts, and in which:

Fig. 1 is a sectional view through a type bar segment showing the mounting of a type bar and its immediately associated operating linkage;

Fig. 2 is a rear plan view of a fragment of a type bar segment;

Fig. 3 is a cross-sectional view on line 3-3 of Fig. 2 showing, moreover, a fragment of a type bar mounted therein;

Fig. 4 is a more or less diagrammatic view of a conventional type bar in relation to its fulcrum wire;

Fig. 5 is an enlarged plan view of a type bar bearing insert; and

Fig. 6 is an enlarged elevational view of the bearing insert of Fig. 5.

United States Patent 0 .It is conventional practice to mount the type bars'of a typewriter in a type bar segment by means of asteel fulcrum wire on which the type bars are adapted to rock. In Fig. 1, a type bar 10 has a type bar fulcrum hole 12 formed in the end thereof which is remote from the type head. A type bar segment 14 (Fig. 2) has formedin the perimeter of the arcuate base thereof a plurality'of slots 15 each of which is adapted to receive the end of a type bar. The slots 15 are intersected by a fulcrum wire groove 17 such that when the fulcrum holes 12 of the type bar are disposed within the fulcrum wire groove 17, a fulcrum wire 16 canbe threaded through the type bar fulcrum holes and through the fulcrum wire grooves 17 of the type bar segment 14. The segment wire 16 accordingly serves as a fulcrum on which the type bars are rocked during the typing operation.

In Fig. 1, the type bar 10 is actuated about its fulcrum into printing position by means of a sub-lever 18, the upper end of which is connected by means of a link 20 to a bell crank lever 22 which is pivoted at 24 to its related type bar 10. The opposite end of the bell crank lever 22 is articulated at 26 to an arm 28 mounted on a fulcrum 30, forming a toggle type bar actuator. A spring 32 normally holds the type bar operating mechanism in the position shown in Fig. 1.

It can be seen by reference to Fig. 2, that the fulcrum wire 16 presents a curved or toroidal surface with the result that the bearing relationship between the cylindrical fulcrum fulcrum holes of the type bars and the fulcrum wire is such as indicated in Fig. 4, wherein it can be seen that by reason of the curved state of the fulcrum wire, three points of contact x, y and z are established between the cylindrical fulcrum hole of the type bar 10 and the fulcrum wire 16. It is obvious that the bearing points x, y and z will be subject to wear, while other of the confronting, though spaced-surfaces, will receive little or no wear. The eccentric relationship of the bearing surfaces will soon result in an enlargement of the fulcrum hole in the type bars such that the type bar will no longer maintain the type face in proper alignment.

The invention herein is predicated on the provision of a true cylindrical bearing surface as the fulcrum for-each type bar. Accordingly, each of the type bars is fitted with a cylindrical bearing insert 38 such as that illustrated in Figs. 5 and 6. conventionally, the fulcrum insert is of such size as to fit snugly the fulcrum wire 16,

and if the fit of the bearing insert on the fulcrum wire is sufiiciently tight, the bearing insert will be held against rotation. In a typical embodiment, the bushing 38 has an external diameter of .187 of an inch and a concentric bearing hole whose diameter is about .094 of an inch.

In order to insure that the bearing insert will not rotate on the fulcrum wire after it has been installed, it may be desirable to form the bearing insert with one or more lateral holding lugs. The bearing insert illustrated in Fig. 6 has a pair of lateral lugs 42 and 44 extending from the opposite faces thereof. The lugs 42 and 44, or either of them if only one is provided, are adapted to seat in a slot 46 (Fig. 3) which intersects the fulcrum wire groove 17. The slot 46 is in the order of .080 of an inch in width and the lugs 42 and 44 should, therefore, be not substantially less in width in order to hold the bearing inserts against rotation.

The bearing inserts may be formed of any suitable material. While steel and steel alloys have been emgood results, the most satisfactory bearing been those molded of relatively'hard organic In this latter category, epoxy resin,

ployed with inserts have plastic materials.

I nylonand a moldable polymer of trifluorochloroethylene, commercially available under the Minnesota Mining and Manufacturing Companystrade name Kel-E, have been Isuccessfullyemployed. Nyl'on lends itselfparticularly and testslmade 'on a complete bar operations maybe expected of a properly fitted in'se'rt.

Not only arising from eccentric bearing surfaces, but it also provides a larger bearing area between the type bar and its fulcrum, thereby better distributing the operating load.

While the fundamentally novel features of the invention have been illustrated and described in connection with a specific embodiment of the invention, itis believed that this embodiment will enable others skilled in the art to apply the principles of the invention in forms departingfrom the exemplary embodiment herein, and such departures are contemplated by the claims.

I claim:

1. In combination, a type segmenthavingan arcuate perimeter provided with type bar slots and, a segment doesthis invention eliminate the difficulties wire groove intersecting said slots, a type bar having a cylindrical fulcrum passage at one end thereof seated in one of said type bar slots, a cylindrical bearing insert within said fulcrum passage, a fulcrum wire in said segmentflwire groove and extending through said cylindrical rotation on said fulcrum wire. V

2. In combination, a, type segment having an arcuate perimeter provided with type bar slots and a segment insert, and a laterally extending lug on said bearing in- 'insert, and means for holding said bearing insert against sert in engagement with said type segment for holding said bearing insert against rotation on said fulcrum wire.

3. In combination, a type segment having an arcuate 1 perimeter provided with type bar slots and a segment wire groove intersecting said slots, a type bar having a cylindrical fulcrum passage at one end thereof seated in one of said type bar slots, a cylindrical bearing insert within said fulcrum passage, a fulcrum wire in said segment wire groove and extending through said cylindrical insert, a slot intersecting said segment wire groove, and a lug on said bearing insert adapted to engage said slot for holding said bearing insert againstlrotation on said fulcrum wire.

4. In combination, a type segment having an arcuate perimeter provided with type bar slots and a segment wire groove intersectingsaid slots, 21 type bar having a cylindrical fulcrum passageat one end thereof seated in one of said type bar slots, a cylindrical molded nylon bearing insert, within said fulcrum passage. a fulcrum wire in said segment wire groove and extending through said cylindricalinsert, and means for holding said bearing insert against rotation on said fulcrum wire.

5. In combination, a type segment having an arcuate perimeter'provided with type bar slots and a segment wire groove intersecting said slots, a type bar having a cylindrical fulcrum passage atone end thereof seated in one of said typebar slots, a cylindrical nylon bearing insert within said fulcrum passageya fulcrum wire in said segment wire groove and extending through said cylindrical insert, a slot intersecting said segment wire groove, and a laterally extendinglug on each of the opposite faces of said bearing insert adapted to engage said slot for holding said bearing insert against rotation on said fulcrum wire.

I References Cited in the file of this patent UNITED STATES PATENTS 913,199 achambeni tnmnsun Feb. 23, 1909 1,206,854 Josleyn ,et a1. Dec. 5, 1916 FOREIGN PATENTS u Germany r Jan. 17, 1910 

